


How Stiles Learned to Love Dog Dick

by halcyon1993



Series: The Kinky Adventures of a Wolf and His Boy [17]
Category: Teen Wolf (TV)
Genre: Alpha Derek Hale, Anal Fingering, Anal Sex, Bestiality, Body Hair, Bottom Derek Hale, Bottom Stiles Stilinski, Breeding, Butt Plugs, Cock Worship, Come Sharing, Deputy Derek Hale, Felching, Fur Kink, Gratuitous Smut, Knotting, Large Cock, Love Confessions, M/M, Marathon Sex, Moving In Together, Multiple Orgasms, Nipple Play, One Shot, Oral Sex, Plot What Plot/Porn Without Plot, Praise Kink, Rimming, Rough Sex, Sex Toys, Sloppy Makeouts, Threesome - M/M/Other, Top Derek Hale, Top Stiles Stilinski, Wet & Messy
Language: English
Status: Completed
Published: 2018-06-18
Updated: 2018-06-18
Packaged: 2019-05-25 02:17:05
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 15,064
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/14966981
Author URL: https://archiveofourown.org/users/halcyon1993/pseuds/halcyon1993
Summary: When Stiles starts dating Derek, he discovers that the alpha is already in a relationship with his dog, a huge English Mastiff named Titan, and he wants Stiles to join them. Once he gets over his initial qualms, Stiles wants that, too.





	How Stiles Learned to Love Dog Dick

**Author's Note:**

> As always with this series, don't judge me for the depravity I have written...
> 
> I can't believe I wrote 15,000+ words of bestiality. :S Well, actually I suppose I can, considering how I have a shit-ton of _Supernatural_ bestiality saved on my computer. But I think there hasn't been anywhere near enough of this particular kink within the _Teen Wolf_ fandom, so I wrote this steaming pile of filth. If any of the subject matter present in this fic grosses you out, don't read it. Any comments that aren't constructive criticism will be deleted. Everyone else, enjoy! :D

Stiles Stilinski couldn't be happier with the way his life is going.

A few months ago, he got the job of his dreams at the Beacon Hills Chronicle. He's starting low on the totem pole, but he is certain that his smarts will ensure a swift rise through the ranks. With a steady paycheque, he was able to afford the rent on a relatively nice apartment where he now lives by himself, a definite upgrade from the shithole he'd previously shared with his best friend, Scott, who is a total slob. And most recently, Stiles has just started dating the gorgeous Derek Hale, a deputy with the Beacon Hills Sheriff's Department. Derek comes from old money, but that wasn't what drew Stiles to him, nor was it his exceptional good looks. No, the first time Derek Hale showed up on Stiles' radar was when he was given his first break by his boss.

He was sent out to cover a robbery currently in progress in a small grocery store and was one of the first on the scene. He witnessed everything—how a man approximately the same age as him held the poor cashier at gunpoint; how the man and the police force were at a stalemate seemingly irresolvable without bloodshed; and how one brave deputy risked his life to sneak into the store's back entrance and singlehandedly apprehend the robber.

That deputy was none other than Derek Hale.

Afterward, when Stiles was lucky enough to snag a quick interview with the hero, Derek asked him out. Derek Hale—a target of lust for basically every eligible person in Beacon Hills—asked _him_ out.

Following such bravery, there was no way Stiles was going to say no.

That was several weeks ago. Since then, he and Derek have gone on multiple dates which all went incredibly well and led to them making things official. They haven't done anything more than kiss and feel each other up a bit over their clothes, but Stiles is very much looking forward to changing that, to touching and licking Derek's awe-inspiring muscles and the monster that he'd felt in his jeans when he'd got a bit more adventurous with his hands at the end of their last date.

So yeah, Stiles would say his life is going pretty damn swimmingly. Barring some horribly cruel twist of fate, he doesn't anticipate anything coming along and disrupting it, and he is practically walking on air on the sunny Saturday morning he makes his way from his apartment building to Derek's house, which is coincidentally just five minutes away. His visit is going to be a surprise, and Stiles can't wait to kiss that surprise off of Derek's stupidly pretty face.

When he turns the corner onto the deputy's street, impatience makes him speed up until he finally reaches the house. He presses the doorbell and waits for Derek to answer, tapping his foot against the doormat. When twenty seconds have passed without anything happening, Stiles looks around to double-check that he didn't just imagine the deputy's Camaro parked in the driveway. He didn't, so he rings the doorbell a second time and listens more closely for any sounds coming from within.

He doesn't hear footsteps or even Derek's dog, Titan, barking. Maybe Derek is taking Titan for a walk or something. How disappointing.

Feeling deflated, Stiles turns around and has just begun walking back down the front path when he hears a crash from inside the house. Thinking the worst, he rushes back to the door, tries the handle and is shocked when it isn't locked. He is trespassing—and in the house of an officer of the law—but he knows that Derek won't arrest him. Especially not when he has such good intentions.

Inside the house now, Stiles can hear more sounds from further in.

They're odd sounds.

Frowning to himself, he grabs the closest object that looks like it could do some damage—Derek's police baton, hung up by the strap on a coatrack—and goes to investigate. He walks with caution, checking through the doorway to the living room as he passes it on his way to the back of the house. When he reaches the kitchen, something else crashes to the ground and he realises that all of the noises have been coming from the first floor. Still, it would be reckless to dismiss anything untoward happening on the ground floor—maybe he has seen too many cop shows—so Stiles makes quick work of completing his circuit and then tentatively puts his foot on the first of the stairs.

"Derek?" he stage-whispers. "Is that you?"

No reply.

Up on the first floor now, Stiles follows the sounds to a door that is ajar. They are clearer now, and Stiles thinks he knows what they are.

The sounds of fucking. The moans are undeniable.

He feels angry that Derek would cheat on him like this, especially not long after they agreed they were exclusive. Lowering the baton to his side, Stiles marches the rest of the way to the door and pushes it open, ready to confront Derek about his unfaithfulness. But the sight he is met with is not the one he was expecting.

On the hardwood floor in front of him is a shattered picture frame, one of the things he heard break. And there, lying at the foot of his king-size bed, is Derek, getting fucked by his dog and looking like he is in heaven. His hands are fisted in the tan fur of Titan's neck and his legs are wrapped around the English Mastiff's hips, holding on for dear life as he is fucked into oblivion. As Stiles continues to watch, Derek lifts his head up off of the sheets and licks at Titan's muzzle. Surely he isn't going to do what it looks like he's going to do.

He does. Titan opens his mouth and licks his owner back, their tongues meeting in a spit-and-slobber filled facsimile of a kiss. It's also filled with the passion of lovers.

Stiles can't believe it.

"Oh my God…" he whispers, too quietly for either Derek or Titan to hear him.

It's only when the baton slips from his limp hand and hits the floor with a loud thump that Derek whips his head in his direction. His hazel eyes are alarmed at first, but they quickly fog over with pleasure again when Titan changes up the way he fucks him, going from short, rapid thrusts to longer, more forceful ones. His eyes roll back in his head and he cries out in ecstasy as something happens that Stiles can't see, and then Titan stops thrusting, his haunches twitching as his cock presumably remains buried in his owner's ass.

While all of this happens, Stiles just keeps standing there, trying to make sense of it.

Derek is having sex with his dog.

Derek is having sex with _his dog_.

It's too much for Stiles to handle right now, so he flees, barely noticing that he is hard in his jeans.

* * *

A couple of hours later, Stiles is sitting on the sofa in his apartment, unable to get the image of his boyfriend getting fucked by his dog out of his mind. Derek isn't a small man by any means, both in terms of his stature and in terms of the magnetic presence his confidence gives him, drawing absolutely everybody's attention whenever he enters a room. But beneath a dog as big as Titan, he'd looked tiny. It made for a striking picture if nothing else.

As the shock of seeing Derek like that finally begins to wear off, Stiles is surprised to discover that he isn't quite as disgusted as he thinks he should be. There are still hang-ups, of course, the thought of how taboo it is and how animals aren't really able to consent. But, God help him, Stiles is mostly curious.

He wants answers, so it's fortuitous that his buzzer goes off just a minute later.

Standing up and traipsing over to his door, Stiles answers the buzz. "Who is it?" he asks into the intercom, thinking he already knows.

"It's…it's Derek," comes the response, just as Stiles predicted. "Can we talk?"

Stiles presses the button that will open the door downstairs and then waits. He hears nothing for a few seconds, and then footsteps getting closer and stopping right on the other side of his door. He expects Derek to knock, but he doesn't, not right away. He must be thinking over what he'll say.

When Derek finally knocks, Stiles opens the door and steps aside. "Come in."

He offers the deputy a drink and ends up making them both a cup of coffee—black for Derek, with milk and several teaspoons of sugar for himself. As he waits for it to brew, he stands with his back to the kitchen counter and looks across the open space of his apartment at where Derek sits patiently on the sofa, in the seat Stiles had just vacated. Derek is dressed in a pair of dark-blue shorts and a loose grey tank top which is clearly an old T-shirt with the sleeves cut off and the neckline widened. The outfit shows off the muscles of his arms and legs, a sight so distracting it nearly makes Stiles forget the reason he has Derek in his apartment.

With a sigh, he turns back to his coffee maker when it finishes, prepares their drinks and joins the deputy on the sofa. He leaves a cushion between them, whereas before he would have sat right next to Derek without even thinking about it.

"Here," Stiles says, proffering a plain white mug.

Derek takes it with a quiet, "Thanks."

In silence both men sip their coffee, each one waiting for the other to speak first. It's Derek who cracks, which makes Stiles glad because it's Derek who has some serious explaining to do.

"What you walked in on…" the older man says, putting his mug down on a coaster on the coffee table. "It wasn't what it looked like."

Stiles snorts. "You mean you _weren't_ letting your dog fuck you?"

Derek winces. "I was, but there's more to it than that."

"This should be good. I'm all ears, I guess."

The deputy blows out a long breath. "There's something I haven't told you about me, about what I am. I was planning on telling you soon, but this has forced my hand."

"What is it?" Stiles prods, intrigued despite himself. He wants to believe there is a good reason for all of this, because he'd liked Derek more than he has ever liked anyone.

"I'll just come right out and say it: I'm a werewolf, and Titan and I are lovers."

Stiles stares.

Then he stares some more.

"What?" he croaks eventually, wondering how Derek managed this long to hide the fact that he is insane.

"I'm a werewolf. And I know what you're thinking, but just trust me," Derek entreaties. "I can prove it."

After putting his own mug down on the coffee table, missing the coasters and not giving a damn, Stiles turns his whole body to face Derek and raises a disbelieving eyebrow. "Get on with it then. Show me this 'proof'," he sneers with a roll of his eyes.

He very quickly finds out that there is much more to the world than he had ever dreamed was possible. Derek's face changes. His eyes, the gorgeous hazel Stiles had found beautiful from the moment they met his, start to glow red. Coarse hair grows down the sides of Derek's face. His brow becomes heavier, shadowing his eyes, and his eyebrows recede entirely. When Derek bares his teeth, Stiles sees that they are no longer human-shaped but sharp and deadly-looking, like a dog's—or a wolf's, he supposes in this case.

"Y-you…" Stiles gapes, lost for words for the second time that day.

The transformation reverts just as quickly as it had come on, and Derek looks at him with those hazel eyes again, filled with nerves. "I'm a werewolf," he repeats.

"Werewolves are real?" Stiles asks, his voice a whisper.

"Yes."

"How?"

"I don't know how. All I know is that we're very real and have been for as long as anyone can remember. The stories had to come from somewhere."

What ensues is a half-hour conversation in which Stiles asks Derek every question that enters his mind, no matter how stupid it sounds. Derek is patient as he answers them all, until Stiles can think of no more that pertain to his lycanthropic status.

"Titan and I," Derek starts, sliding a tiny bit closer on the sofa, "we're not what you think."

Stiles recalls what the older man said earlier. "You're… _lovers_." The word sounds wrong.

"We are."

"But a dog can't…"

"He can."

"What, is Titan a weredog or something?" Stiles' tone is derisive.

"No, he's a regular dog. But me being a werewolf, and an alpha at that, means I have an…an affinity, if you will. He can't speak and I can't hear what he's thinking, if he's even thinking words, but I can still understand him and he still understands me, y'know?"

Stiles doesn't, but he nods anyway. "Right."

"I got him a few years ago, a rescue. His old owners were abusive and he would've been sent to a shelter, but something about him called to me."

"You wanted him," Stiles guesses.

"Not immediately, but I loved him from the start. And once I gained his trust, he soon loved me. Looking back on it now, I guess it was inevitable that we'd fall into bed together at some point."

"You're speaking as if he's a person."

"He's not human, but he's no less important to me, nor me to him," Derek defends.

Stiles' mind supplies him with an image of what he'd witnessed in Derek's bedroom and he has to admit that what the deputy is telling him fits. There was passion there, not just mindless, animal fucking, as absurd as it sounds. Maybe Stiles is going crazy, too.

"And me? What was I going to be?"

"When I met you, I knew you'd be just as important," Derek answers, sincerity in his eyes. "And after the first time I brought you to my place, I could tell that Titan was just as enamoured."

"So you weren't just playing with me?" Stiles enquires, his voice hurt now, the fear he'd had before he found Derek with Titan and not another person coming back to him.

"No!" Derek denies instantly. "I would never do that."

"Then what was it?"

"When I thought you were ready, I was going to ask you to join us."

Stiles' eyes become as round as saucers. " _Join you_?"

"Yes. We want you to be a part of our relationship, to love us and let us love you in return."

"And when you say 'love'…"

"I mean all of it—dates, romance, companionship and sex. All of it."

"I don't know if I want that," Stiles admits, though he is loath to do it because he still doesn't want things to end between him and Derek.

"It's okay. You don't have to say yes right away. I can be patient, and I'm more than capable of keeping Titan occupied. All I ask is that you don't tell other humans. They wouldn't understand." Derek covers Stiles' hand with one of his. Stiles doesn't move away. "Call me when you've decided."

With that, the deputy leaves, his mug only half-empty.

Stiles, now alone with just his thoughts for company, tries to busy himself, not wanting to think about what Derek has just revealed to him, the choice he was given, or the way his body reacted to what he found happening in Derek's bedroom, which he'd been staunchly avoiding ever since he came home. He tips the rest of their coffees down the kitchen sink, washes out the mugs and puts them in the drying rack on the counter, but then that's everything. There are no other chores left to do because he hasn't let any part of his apartment get dirty for longer than a few hours, and he doesn't think that watching TV will be enough to occupy him.

He has no choice but to think about it.

He doesn't want to lose Derek, he knows that for sure. And as horrified as he should feel about it, and although he still has some misgivings, he has to admit to himself that seeing Derek being fucked like that was…hot. Was it just Derek, or was it Titan, too? He knows the answer, and most people would call it the wrong one.

Stiles is ashamed of himself and looks around his apartment as if anticipating it suddenly filling with people staring at him with their faces full of judgment. When nothing of the sort happens, he returns once more to the sofa and lies lengthways across it, on his back with an arm thrown over his eyes. He already has his answer, but he doesn't do anything about it just yet. Derek said he had time.

* * *

The very next day, Stiles again makes his way to Derek's house.

He is very anxious, wondering what Derek will be expecting of him once he tells the deputy that he wants to keep seeing him. Will he be expected to engage with Titan straight away? Or will Derek be lenient enough to let him work his way up to it? And if Stiles never manages to gather his nerve, will that be the clean-cut end of their relationship, just after they truly began? Stiles thinks he already knows the answer to that question, and it's yes. With how fond and loving Derek's face had become when he spoke of his 'relationship' with Titan, there is no other answer.

The way Stiles feels when he reaches Derek's front door is such a contrast to the previous day. It's jarring. Before he can gather enough nerve to knock, the door opens to reveal Derek standing on the other side in a pair of grey sweatpants and an old white T-shirt. He doesn't seem surprised to see Stiles on his doorstep.

"Werewolf senses," he explains as if reading Stiles' mind.

"Oh."

"Want to come in?"

"Yes. Please."

Derek steps aside and closes the door behind them. When he walks into the living room, Stiles spots Titan lying at one end of the large leather sofa.

"Ignore him," Derek says with a smile in his voice. "He's being a huge grump today."

Titan growls quietly, causing his owner to chuckle. Derek sits on the cushion next to the dog and scratches behind his ear. "Yeah, yeah, whatever you say, you big lug." He gives him one final scratch before turning back to Stiles. "Don't be shy; have a seat."

Stiles does so, taking up the third and final cushion.

"So…have you made a decision already?" Derek asks him. "I thought it would take you longer."

"So did I, honestly," Stiles responds, twisting his hands together in his lap. "But yeah, I've decided."

"What's it going to be?"

Derek is hiding it well, but Stiles can still see the hope and apprehension warring in his eyes. He immediately wants to allay the latter emotion, so he gives his verdict quickly: "I want to try," he says, his gaze darting back and forth between Derek and Titan's faces. "I'm still not really sure how it would work, but I can't deny that I'm interested. But I want to ease into things, if that's okay."

"That's more than okay, Stiles," Derek grins, surging forward and kissing the living daylights out of him.

When this kiss ends, Derek leans against the back of the sofa and pats the space between himself and Titan, a gesture that is clearly an instruction for the dog. Titan stands up and moves closer, resting his forepaws on Derek's thigh as he allows the alpha to plant a kiss on his muzzle. It isn't like the one they'd shared when Stiles walked in on them, all tongue and slobber. Both of their mouths remain closed, and yet it retains the same striking level of intimacy.

Pulling away from Titan, Derek turns to look expectantly at Stiles. It takes a few moments for the human to figure out why, and once he does he swallows tightly and nods, mostly to himself. Derek gets up from his cushion so that Stiles can take his place, and the aspiring journalist considers saying that he isn't completely comfortable doing this yet, but the expression on Derek's face is now one of such happiness that he can't bear to destroy it.

After taking just enough time to give himself a pep talk in his head, Stiles brings his face close to Titan's and mirrors what Derek just did.

Right away, the alienness of what he is doing gets to him. He had an idea of what it would feel like, but the reality is harder to swallow than the expectation. It's weird feeling fur, long whiskers and jowls instead of soft lips against his and the scratch of Derek's stubble against his cheeks, but Stiles sticks with it for a few more seconds before finishing his first kiss with Titan. The wetness of the dog's nose leaves his upper lip cold, but it isn't as unpleasant a sensation as he would have thought, and then Derek draws him back against his side, starts running his fingers through his hair and Titan drapes himself across both of their laps, so Stiles doesn't really have the mental capacity to ruminate for very long.

All in all, he is pleased with how everything went.

* * *

After that visit, Stiles goes over to Derek's house more and more often to hang out with him and Titan. It's shocking how swiftly he gets used to how the two now interact around him, how open Derek is with his affection for Titan and how he tries to include Stiles in things, too.

During this time, Stiles' sick curiosity grows. It's a disease that had previously been hiding behind some door in his mind, and walking in on Derek and Titan that day busted the door down. One evening, Stiles sits against the pillows in his bed, his laptop open next to him. It's hot even with air conditioning, so all that covers him is a pair of thin Batman boxers he has had for years. He should be writing a fluff piece for the Beacon Hills Chronicle, but Stiles' mind wanders and he can't stop himself from opening a new incognito window in his web browser and doing some…research.

Yes, he'll call it research.

It's not too hard to find what he is looking for; you can find anything on the Internet these days, something he already knew very well. Stiles almost doesn't want to blink when he clicks on a link and ends up on a webpage which contains multiple videos all posted by the same user, someone called 'dogcocklvr83'. They range from two to ten minutes in duration, and the thumbnails give small previews of the depraved acts carried out within by a man and his two male dogs.

In all of the thumbnails, and Stiles guesses in the videos themselves, the man's face is blurred out to protect his privacy, but Stiles isn't interested in him. All of his focus is on the other subjects of the videos: the dogs. One is a grey Great Dane, and the other is a shaggy black Newfoundland. Both large, like Titan, and in the Great Dane's case, even larger.

His heart beating fast in his chest, Stiles clicks on one of the thumbnails at random and settles in to watch the events play out.

It starts with the blurry-faced man on his knees, his hand out of frame as he adjusts the angle of the camera. When satisfied, he crawls backward, whistles and says, "Here, boys," to something also out of frame, and then the two dogs bound over to him, the sound of their paws soft on the pale-blue carpet. Both dogs enthusiastically lick their owner's face, their tails wagging so quickly that they're a blur as well, and then the man pushes the Great Dane away and gets down on his hands and knees, his ass pointed toward the Newfoundland. He reaches behind himself, pulls a black butt plug out of his presumably lubed and stretched asshole, and then the Newfoundland takes over, apparently already knowing to mount from previous videos they have recorded.

Stiles cups his growing erection through his underwear when he sees the Newfoundland's cock emerging from its sheath, his hips moving like he is already fucking a bitch as he tries to get inside his owner. The shape of it is foreign and intriguing to him, as is its colour, a shocking red. He wonders if Titan's cock looks like that just as the man reaches behind himself again, takes his dog's dick in hand and helps guide it to its target.

As soon as the Newfoundland feels wet heat around him, he starts thrusting wildly, making his owner cry out.

Stiles watches in awe and pulls his cock out through the flap in his boxers to stroke it.

The Newfoundland keeps fucking the man hard, but the man quickly gets over the surprise of it and lifts his head to locate the Great Dane. Said dog lies on its side on the floor in front of him, and when he whistles again, the sound weaker this time, the dog lifts one of his legs in the air and Stiles gapes when he sees its cock.

 _Jesus Christ_ , it's massive, looks like it would tear the man apart.

"Oh fuck…" Stiles breathes as the man carefully bends down and wraps his lips around the Great Dane, giving a blowjob to one of his dogs while the other fucks him.

Stiles has never been so turned on in his life, which means it's over very soon after that. A couple of absentminded tugs on his cock is all it takes for him to come. He splatters his front with his jizz as the threesome continues to have their fun on his laptop screen, the video not even halfway over. As soon as he comes down from his high, Stiles stops the video and pushes his laptop away from him, shuddering as shame washes over him and makes his skin itch. He loved watching that man getting fucked by his dogs, and that's the problem, isn't it?

It's wrong. So fucking _wrong_. Stiles would say that most of the rest of the world would agree.

But then he reminds himself of how enthusiastic Titan had been when he fucked Derek. If he didn't want it, he wouldn't have acted like that. Right?

Plus, Derek had promised him that, thanks to his status as a werewolf, he can read Titan like a book. They can communicate on a deeper level than a dog and a mere human, and Stiles trusts Derek enough by now to believe that he was telling the truth.

Reminding himself of this makes Stiles feel much better as he uses the box of tissues on his bedside table to clean himself up. All in all, he'd venture that this evening helped him a lot, mainly to confirm and begin coming to terms with his attraction to dogs. He isn't sure if he can leap right into things like he knows Derek would like him to. He would probably freak out if he tried, end up doing something stupid that would lead to him never seeing Derek again. And like he has told himself several times since finding out about Derek and Titan, that is the last thing he wants. He'll keep easing into things.

He'll get there.

* * *

Despite Stiles' new acceptance, progress is slow for the next few weeks. He sees Derek and Titan nearly every day and sleeps over at Derek's house more often than not, where he and Derek keep fooling around with each other—without the dog for now, to Stiles' relief. Derek always goes to bed in just his underwear, but Stiles always keeps a borrowed T-shirt on when they cuddle up together beneath the covers. Titan sometimes curls up at the foot of the bed, but other times he wiggles beneath the covers as well and Stiles falls asleep to the weight of the dog's head on his stomach. It's nice, and something he can definitely get used to.

It's in month five of his relationship with Derek that things start changing.

The catalyst is entering Derek's house with the key he was given not too long ago to find the werewolf and Titan fucking in the space between the coffee table and the living room sofa, the dog up on Derek's back this time. Stiles is no less entranced by the spectacle they make like this, but this time he doesn't run, doesn't even think of it. Nor does he avert his gaze. He watches openly as Derek, never raising his head, makes the most amazing whimpering sounds and gouges his claws into the hardwood floor, as Titan thrusts with fervour into the clutch of his owner's ass, his long tongue hanging out of the side of his muzzle.

It's Titan who first sees their audience. The English Mastiff looks at Stiles and fucks Derek even harder, his eyes becoming almost smug when the increased speed only an animal could be capable of makes Derek wail loudly, his arms shaking as he supports both of them. Maybe Stiles is just seeing things, but there is also a challenge in Titan's eyes, like he is daring him to actually do something this time.

Stiles is still a bit skittish about actually participating, but he wants in. God, does he want in.

Hesitantly, he steps fully into the room. He can smell it now, the scent of sex and sweat. It's intoxicating, goes right to his head and goes a long way to eradicating the inhibitions that have been holding him back. He keeps walking and doesn't stop until he sits down right in the middle of the sofa, giving himself a front-row seat to the show.

Titan keeps staring at him, and Stiles stares right back as he reaches out and touches his side.

The dog's fur is soft beneath his palm. Not for the first time, Stiles wonders what that fur would feel like against other parts of his skin, rubbing against his back or maybe the insides of his thighs if Titan were to mount him like he'd mounted Derek when Stiles first saw them having sex. He strokes his hand down Titan's flank until he reaches his haunches, just lightly resting it there and feeling the way the dog moves them rapidly, sending shockwaves up the length of his arm. Stiles has bottomed before, but never has he been fucked as hard as Derek is getting fucked in front of him.

His asshole clenches sympathetically.

Stiles leans back again, pulls himself out of his chinos and jerks off to the sounds, sights and smells assaulting his senses. It's so much better than a video on the Internet. Titan's eyes go to his hand on his cock, and when his foot accidentally bumps against Derek's wrist as he spreads his legs to get more comfortable, the werewolf's head snaps up to look at him as well, finally realising that he is no longer alone with his dog.

Derek's face is flushed a pretty red. His lips are swollen and parts of his beard are shiny with slobber, presumably from when he'd made out with Titan before moving onto the main event.

Stiles doesn't know whether to look at Derek's face or Titan's as he jerks off. He ends up flicking his eyes between the two until the latter's thrusts get longer and more forceful like they had up in Derek's bedroom. Thanks to his research, Stiles now knows what this means—Titan is trying to force his knot past the resistance of Derek's asshole. He soon finds success, and at the same time Stiles glimpses Derek splattering the floor with his thick alpha seed, coming untouched.

The sight of something so glorious is what sets Stiles off as well.

He spurts all over his hand, some of his load dripping down to stain his chinos. It's tough to keep his eyes open but he manages to do so, not willing to take them off of Derek and Titan joined like this.

When his orgasm is over, Stiles holds up his soiled hand and wrinkles his noise at how much he'd come all over himself. He searches around for something he can use to clean it off, but he doesn't find anything within reach, no box of tissues here. In doing so, he stops looking at Titan and Derek, and he is startled when he feels the dog licking at his hand. Stiles is stunned as Titan laps up his come, and he thinks somewhere in the back of his mind that the dog is probably used to tasting semen. It's usually Derek's he cleans up, though.

When most but not all of his come is gone, Stiles is momentarily confused when a breathy Derek orders Titan to stop. His confusion clears when he sees the hunger in Derek's eyes.

"You're both kinda filthy, aren't you?" Stiles mutters as he lets Derek eat the rest of his come.

"Of course we are," Derek answers between licks. "Dirty sex is the _best_."

Stiles hums, taking back his hand when Derek finishes. "Mmm, I wouldn't really know."

"No?"

"All the sex I've had in the past has been kinda vanilla—especially compared to, y'know, all of this." He gestures between Derek and Titan.

"Hmm…we'll have to remedy that soon, then."

Stiles nods. "Definitely."

* * *

From then on, Derek and Titan don't try to hide the amount of sex they have. Stiles is at first flabbergasted, not really knowing how the hell either of them could have the stamina to keep up with the other. It also means that, when he and Derek have had sex without Titan, Derek was holding back. Stiles is slightly miffed but gets over it and can't wait to be worn out by both of them when he finally works up enough nerve to bring Titan into the bedroom with them.

Exactly a week after Stiles walked in on Titan and Derek going at it for the second time, they show up at his door unannounced. Derek is dressed in his deputy uniform and holds Titan's leash in one hand. A bag filled with God knows what dangles from the other.

"Uhh…what're you doing here?" Stiles asks the alpha, letting them inside. "Not that I'm not glad to see you."

"I have to leave town for a couple of days for work," Derek explains, setting the bag down just inside the door, "and I was wondering if I could impose on you to watch Titan until I get back."

"I guess so," Stiles answers. He knows he has made the right choice when Derek's face lights up with a grin, an expression Stiles always wants to see.

"Awesome. I've got a bunch of his stuff in here, his favourite toys, some food, a new roll of poo bags. I usually walk him twice a day, but he can manage with just one if you can't fit two in around work."

Stiles listens attentively as Derek tells him everything he needs to know to care for Titan, his feeding schedule, how much food to give him etc. When Stiles thinks he has all the information he needs, he gently pushes Derek toward the door with several reassurances that he'll be able to handle it for however long he needs. "Don't worry about us," he says, squeezing one of the older man's hands. "I think I've got it all covered."

"Are you absolutely sure?"

"Yup." Stiles leans down and ruffles the fur on top of Titan's head. "We'll have a blast, won't we, Titan?"

The dog's tail thumps against the floor as he wags it.

"Alright. Call me if you have any trouble."

"Relax, Der." Stiles kisses him chastely. "We'll be fine. Besides, this could be a good chance to get better acquainted."

Derek's eyes widen infinitesimally. "You mean…?"

"That's exactly what I mean. I might even send pictures if you leave now." Stiles winks.

That's all it takes to get Derek out the door.

Alone with Titan, Stiles slides the deadbolt into place and spins on his heel to find the dog inspecting the apartment, sniffing everything within reach. Titan has never been to Stiles' place before, so he leaves him to it, picks up the bag Derek left behind and walks over to the kitchen to prepare some dinner for the two of them. He is feeling lazy so he just cooks some chicken noodles for himself and, as per Derek's instructions, puts a precise amount of Titan's dog food into his red dog bowl. He sets the latter on the floor next to the sofa, swiftly moving away when Titan bounds over to it and shoves is snout right in it, and takes his place on the sofa with his bowl of noodles balanced carefully on top of a cushion in his lap.

"What should we watch?" Stiles asks, flicking through the channels on his TV. Titan is too busy scoffing down his dinner to even acknowledge that his temporary caretaker made a sound, so Stiles continues pressing the button on his TV remote until he comes across a _Supernatural_ rerun, one of the episodes from the fifth season. Stiles hasn't seen the older seasons in a while, so he drops the remote next to him and makes a start on his own dinner.

When the episode ends, both Stiles and Titan have finished eating, so he washes up their bowls, puts them in the drying rack and then thinks it's time to move on to the fun.

"Titan, come here, boy!" Stiles beckons.

The dog leaps up from his spot in front of the sofa, tail wagging already. Stiles gives him some fuss before leading him across the apartment to his bed, which is partially hidden by a screen. He climbs onto the mattress and waits for Titan to do the same, at which point he is bowled over as the dog seems intent on licking his face. Stiles gags at the stench of dog food on Titan's breath, but he endures and rubs his hands up and down his flanks as he begins licking back, copying what he has seen Derek do several times now. It's even weirder than the close-mouthed kiss they'd shared when Stiles agreed to give them a shot, but that's to be expected, he supposes.

"Alright, alright!" he exclaims with a laugh, pushing Titan away from his face. "Give me a second!"

When Titan moves away a few feet, Stiles strips out of all of his clothes and immediately calls him back, wanting to experience skin on fur.

It's every bit as exquisite as he had guessed it would be.

On his back again, Stiles uses Titan's collar to pull him on top and wraps his legs around his hips, again copying Derek. The dog must figure out what is going on after that, because Stiles can feel something hard poking his perineum when their bodies rub together. He knows what that something is and wants to see it, so he releases the dog and pushes him onto his side. His cock drips pre-come onto the sheets as he stares at Titan's furry sheath and balls. There is something about them that's so attractive to him, and he has to get his hands on them now.

He cradles Titan's balls in the palm of his hand. They feel heavy and soft, surprisingly large even for a dog of Titan's size, and Stiles knows that they are full of thin dog come ready to breed up a bitch in heat. He feels like one in that moment.

Derek already knows what that feels like, to be fucked hard and put away wet by Titan. Stiles is incredibly jealous and wants to experience what that's like as well, but he won't try today. He wants Derek there for his first time with Titan. As much as he craves it, he'll probably be nervous and flighty when the event is about to go down, and he would prefer to have Derek there to keep him calm and guide him through it with words and gentle touches, which, as a dog, Titan just can't give him.

Releasing Titan's balls, Stiles moves on to his sheath. Like he'd felt before, the tapered tip of Titan's pinkish-red cock already peeks out, and more emerges when Stiles grips it lightly and rubs his thumb back and forth around the hole of the sheath.

"So hot…"

When all of Titan's cock is out of its sheath, Stiles approximates that it's eight inches long and very thick for a dog. It's smaller than the Great Dane's cock from the video, but Stiles bets it can still do some serious damage, especially when the knot at the base is brought into the equation. Stiles squeezes this misshapen ball of flesh experimentally and snatches his hand back when Titan whines sharply and a thin jet of pre-come spurts from the tip of his cock. He worries for a moment that he has done something to hurt the dog, but then Titan whines again, this time quieter, and wiggles his lower half even closer to Stiles, a clear sign to continue.

The human wraps his hand around Titan's cock and leans in close to examine it. It's covered in thin spiderweb veins and feels so different from his own. There is no skin to move over hardness beneath. It's totally solid, and Stiles has to use some of Titan's pre-come to ease the way as he strokes up and down its length a couple of times, testing it out. While different, it still feels nice and so Stiles has no trouble moving his hand a bit quicker, cupping Titan's balls again with the other.

"That feel good?" he asks Titan when he notices his hindquarters twitching like he is trying to fuck into Stiles' grip but can't manage it in his current position. He should feel stupid talking to the dog like this, but he doesn't.

Titan gives a soft growl, more of a purr than anything, which Stiles guesses means yes.

"Okay then."

He keeps jerking Titan off for a couple of minutes, until he recalls that he hadn't just wanted to use his hand. Once he is sure that Titan won't move too much, Stiles lies down on his front and brings his face mere inches away from the canine's cock. The smell is musky and foreign. There is no escaping the fact that it's a dog's junk he is smelling and not a human man's, but Stiles thinks he likes it well enough anyway.

He grasps the base of Titan's cock, in the small space between the knot and the sheath, and angles it so that he can get his lips around the tip. Again it's alien to him, the shape and texture unlike anything he has had in his mouth before. And the taste…Stiles doesn't know why, but he'd thought that Titan's pre-come wouldn't taste that different from a human man's, but he was mistaken. It's thinner, he already knew that, but the taste still surprises him. It's stronger somehow, or maybe that's just because he is paying such close attention. It's bitter and on the verge of being unpleasant, but the sheer act of doing something so depraved makes it bearable.

For the next couple of minutes, Stiles works his mouth down Titan's eight-inch cock until it reaches his throat, and then he goes even further. His lips bump against the knot and there is no way in hell he is getting them around _that_ , so he retreats and repeats the process all over again, giving a dog a blowjob. The thought sends a thrill through his body, and he stops briefly to snap up his phone from the nightstand. Once he has the camera app open, he resumes blowing Titan and takes a few pictures which he sends to Derek after cropping the top half of his face out of them, just in case someone other than Derek sees them.

Once they are sent, Stiles throws his phone onto the pillows and focuses all of his attention on making Titan come. He starts to squeeze the knot in time with the bobbing of his head. The dog approves of this, if his ensuing bark and the way the twitching of his haunches gets worse are anything to go by. He keeps squeezing at fluctuating strengths, trying to simulate what it would feel like to be locked inside a bitch's cunt—or in his or Derek's ass.

It does the job.

Before Stiles can prepare himself, Titan all but howls and his cock seems to get even bigger as he floods Stiles' mouth with watery seed, making him pull off choking and sputtering. He snaps his eyes shut just in time to avoid getting any come in them, and then, still keeping a hand on the knot, he rolls onto his back and directs the tip of Titan's cock at his neck and chest, letting himself be painted with come. The stench of it is overwhelming, like Titan's sex but multiplied a hundred times. Like the taste, it verges on nauseating, but thankfully it doesn't actually get there.

For several minutes Stiles is showered in dog come as Titan bucks into his grip, and then the spurts lessen and stop altogether, so he releases him and quickly jerks himself off. It doesn't take long at all for him to come as well, and then he just lies there for a while as jizz dries all over his skin like some sort of sick moisturiser he is trying out.

"I'm totally gonna have to replace my whole bed after this," he complains, noting how it's now basically a lake of dog jizz.

Titan, in between cleaning himself, looks up at the sound of his voice.

"Yeah, yeah, I know…" Stiles continues as if they're having a conversation. "Good thing I've got a steady job now and can actually afford it. I guess this is why you normally come inside Derek, huh?"

Another look, this one Stiles thinks says, "Well, duh."

"Lesson learned."

Since the sheets are already ruined, he kicks Titan off of the bed and uses the parts that aren't already soaked to wipe himself off. Then he balls everything up, puts it inside of a black trash bag to dispose of the next day and turns to his bare mattress. The pillows will survive, but just like he'd thought, the mattress is going to be stained beyond saving. Besides, Stiles doesn't particularly want to sleep surrounded by the musk of Titan's jizz all the time.

"Yup, definitely a new mattress."

He sleeps on his sofa that night.

* * *

"I think I'm ready," Stiles tells Derek the day after he gets back into town. They lounge together on Derek's sofa, the latest _Avengers_ movie playing on the TV. The alpha sits at one end, Stiles sits diagonally with his back against Derek's chest, their heads resting together, his right leg on the sofa and the other on the floor, and Titan is dozing lightly in the space between Stiles' right leg and the back of the sofa. The dog's head rests on Stiles' thigh. He looks far too adorable for a dog of his considerable size.

"Ready for what?" Derek asks him, not catching on.

"To go all the way with both of you."

Derek's whole body briefly goes rigid before he relaxes it again. "You sure?"

"I'm sure."

Derek kisses his temple. "Alright. We'll do it tonight. Okay?"

"Okay." Stiles closes his eyes. "You'll be there the whole time, right?"

"I wouldn't be anywhere else."

* * *

Two hours later, it's finally time.

It's been over five months in the making, and as Stiles stands naked in Derek's en suite bathroom and looks at his reflection in the mirror above the sink, he knows there will be no turning back after tonight. There will be no way to forget what it feels like to have a dog's dick inside of him. He prays to anyone who will listen that he will like it as much as he is banking on liking it. He has too much riding on this for it not to work out.

Maybe he could fake it if the fantasy is all that works for him and not the reality, but he is sure that Derek will be able to tell. And maybe they could make it work with just him blowing Titan and nothing more, but Derek has made it clear that he wants them to share everything with each other.

And if Stiles is honest with himself, he wouldn't be content with anything less either.

"You've got this," he tells his mirror self, not thinking about how Derek will be able to hear him. "It's gonna be great."

When he exits the bathroom, Stiles is greeted by Derek lying on his bed with Titan's head between his legs, the dog's long tongue lapping at the tip of his uncut cock. "Got started without me, huh?"

Derek grins. "Couldn't help myself. Come on. Get in on this."

Already feeling more at ease, Stiles walks over to the bed and climbs onto it. He positions himself next to Titan and starts worshipping Derek's seven-inch cock too, their tongues warring to taste the deliciousness of his pre-come as it beads at the slit. Derek moans and shifts slightly to get more comfortable, one hand tucked behind his head to support it so that he can see better and the other around the base of his cock, holding it steady.

"You two look so good together," he comments, his pupils blown.

Stiles smiles bashfully and lets Titan have the tip of Derek's cock, choosing to go further down and suck one of the alpha's hairy low-hanging balls into his mouth instead. This gets him another moan, louder this time, and in turn the sound spurs both him and Titan on even more, both of them wanting to pleasure Derek as much as they possibly can—Stiles because he wants to show Derek how much he appreciates his patience; Titan because he wants to be a good boy and earn his owner's affection. He alternates between Derek's balls because they're too big to both fit inside at the same time, and the taste of the slightly sweaty skin is enhanced by drops of dog drool as they run down the length of Derek's cock from where Titan still licks messily over the tip.

Soon, Derek moves again, sliding out of Stiles' reach. Titan tries to follow, but his owner holds up a hand and commands him to stay where he is.

"So, how do you want to do this?" Derek asks Stiles, stroking himself with the aid of Titan's drool.

Stiles shrugs. "I don't know. You're the one with the experience here, so you tell me."

Nodding, Derek reaches for his bedside table and takes a tube of lubricant out of the top drawer. "If it's alright with you, I think we should start with some rimming, let Titan get familiar with the smell and taste of you, before I open you up with my fingers."

His nerves threatening to creep in again, Stiles says yes before he can think too much on it.

With Derek's assistance, Stiles finds himself in the middle of the bed on his elbows and knees, his back arched so that his asshole is exposed. It's an incredibly vulnerable position to be in, but Derek, who kneels next to him with Titan, runs a hand up and down his trembling back and he is soothed enough to continue.

"Here, Titan," Derek calls, using his index finger to lead the dog's nose to Stiles' asshole.

Stiles startles when he feels the dog's hot breath against him, but Derek does a good job of keeping both of them calm.

"Easy, boy," the alpha says fondly. "Don't want to freak your new mate out, do you?"

"He's done this to you before, right?" Stiles asks him.

"Yes, many times. Gonna feel so good. And don't worry—I'll stop him from trying to mount you before you're ready."

"R-right."

The first swipe of Titan's tongue is odd. It of course feels nothing like a human's, and it takes a few seconds for Stiles to see past that and realise how pleasurable it still is—and the added benefits it has, like its strength. Titan pushes against Stiles' tight rim with a surprising amount of force, like he knows from the times he has rimmed and fucked Derek that he can get inside if he just pushes hard enough. Stiles' asshole is soon drenched in slobber, which helps to slick the way the first time he feels Titan's tongue slip briefly inside of his body.

"Feels good, right?" Derek says amusedly.

"Yeah…" Stiles answers breathily, hanging his head so that he can see Titan between his own legs. Beneath the fur of Titan's belly, he just can just about see the tip of the dog's cock.

"Just wait until he fucks you, Stiles. You don't even know…" Derek kisses his shoulder. "Forget the other times you've bottomed. This'll be nothing like that. It'll be hard and animalistic as Titan breeds you up like his new bitch, but the connection you feel when he's inside you…there's nothing like it. You'll see."

After a while longer of Titan rimming him, Derek urges the dog away and takes his position with the lube once again in hand. Stiles hears him pop the cap, the slick sounds of him getting a couple fingers ready and then he feels one of them at his hole. Derek runs it in circles around his rim, waiting for Stiles to unclench and let him inside. All the while he murmurs more words of encouragement, telling him how amazing he is going to look with Titan on top of him, how happy he is that Stiles is doing this for him, how happy the three of them are all going to be together.

With these words to distract him, it's easy for Stiles to relax and then Derek's index finger slides in deep, making him gasp. It's not painful but it's not exactly pleasurable either, at least not until Derek curls his finger and strokes over his inner walls, searching for his prostate. When he finds it, the alpha goes to town on it, rubbing back and forth across it every time he shallowly thrusts his finger and even scratching his short nail against it.

Stiles is soon barely able to hold himself up, but he manages because he doesn't want to accidentally pull away from Derek's finger, taking the pleasure away, too. "Der…" he breathes, unable to close his mouth.

"You ready for another one?"

"Yeah…give it to me."

One finger becomes two, and then three and even four when Derek slips his pinky finger in alongside the others.

"Do you want me to fuck you first?" Derek asks him, moulding his front to Stiles' back.

"I wouldn't say no," Stiles answers, turning his head and meeting the alpha in a sloppy kiss.

"It'll help, get you stretched out a bit more so you're really ready for Titan. You probably already know from watching him fuck me, but he'll go hard right from the start."

"Yeah…yeah, I think you going first would be good."

Derek kisses him again before sitting back on his heels and slicking up his cock. "I'm gonna push in now. Tell me to stop if you need me to."

Stiles looks back over his shoulder and raises an eyebrow at the werewolf. "I've bottomed before—for you, in fact. Or have you already forgotten?"

Derek rolls his eyes. "Forgive me for trying to make this as comfortable for you as possible," he snarks.

With a snort, Stiles looks back at the headboard. "And I appreciate it."

"You'd better."

Slowly Derek starts to enter his human lover. Stiles fights not to tighten up his hole again as inch by torturous inch slides inside, until finally he has been fed all seven and he can feel the scratch of Derek's pubes against his cheeks.

"You good?" the alpha enquires.

"I'm good."

"Can I move?"

Stiles experimentally clenches down on Derek's thick cock and nods when no pain occurs. "Yeah."

"Thank God."

After he puts his hands on Stiles' hips, Derek's first few thrusts are gentle, tentative, like he is waiting for the younger man to rescind his permission at any moment. When Stiles does nothing of the sort, Derek seems to grow more confident that he won't hurt him and moves quicker. He plasters himself to the human's back once more and kisses at his neck, sucking on skin and worrying it between his thankfully blunt teeth to leave what will no doubt turn out to be one hell of a hickey.

Stiles tilts his head to the side to give the alpha better access, losing himself in being filled nice and deep, in the smell and heat of him. He doesn't even think about what Titan is doing with his two human lovers wrapped up in each other, not until Derek suddenly jolts above him, stops adorning Stiles' neck with more marks and stops thrusting into him.

"What is it?" Stiles asks, wondering why the werewolf ceased moving.

"Titan's licking my ass," Derek replies after a broken moan. "I'll never get tired of his tongue."

Stiles moans himself at the image that appears in his mind's eye. "I wish I could see."

Derek doesn't move again for a couple of minutes, and when he does he is back to the slow thrusts, maybe two inches of his cock leaving Stiles' hole with each one. "Don't wanna dislodge him," is his explanation.

Just when Stiles is getting impatient, his desire to be fucked harder overriding his patience, the weight on his back doubles and he nearly face-plants into the sheets.

"What's going on?!"

"Titan—"

Derek manages to get out that one word before he chokes on the rest of his sentence and his nails dig almost painfully into Stiles' hips.

"Derek? Talk to me!"

"It's Titan. He's—"

Stiles thinks he can guess now. The way both of them are being jerked about is a dead giveaway. "He's fucking you, isn't he?"

"He's trying."

"You're not prepped, are you?"

"No…but I can take it. Sometimes a little pain's good. I guess he got tired of waiting for his turn with you."

Stiles' legs shake because holding up himself, Derek _and_ Titan is a lot of weight for him to bear. He groans into his bicep as Titan presumably forces his way inside Derek's tight hole and starts up frantic thrusts that in turn cause Derek's cock to move inside of his hole, too. He can barely think because the alpha is right up against his prostate, and he wonders how they must look right now: Stiles on the bottom of the pile, Derek's bigger body on top of him, and then Titan, a huge dog, on top of both of them, fucking his owner. Stiles feels like he could come untouched then and there, even though he has never accomplished such a feat before.

An indeterminate amount of time passes without anything changing. Stiles stays right on the precipice, unable to actually go over, Derek stays buried inside him, and Titan keeps fucking into Derek with abandon, an animal without thought for the hole he is ruining. It's so hot that Stiles doesn't register a change that happens until Derek abruptly pulls out of him, leaving him feeling empty.

"Wha—?" he asks, nearly incoherent.

"I ordered him to stop before he could knot me," Derek says, turning him onto his back. His face is red from being fucked hard.

"Oh. Why?"

"Because he still has to fuck you. That's what this was all about, remember?"

Stiles does, somewhere in the back of his mind, in the space that isn't fogged by lust. "Oh. Cool."

"You still up for it?"

"Yeah…feel empty," Stiles whines.

"Titan's got you covered."

Derek carefully drags Stiles to the foot of the bed and holds his legs back for him, mirroring the position he'd found Derek in when this all started. Turning his head to the side, Stiles looks with bleary eyes at where Titan paces restlessly back and forth across a small stretch of the mattress, his hard cock bobbing beneath him. He is obviously put out at being forced to stop fucking one of his bitches.

Once Stiles has enough wherewithal to hold his own legs back, his hands behind his knees, Derek leaves the bed and calls Titan to him.

"Get ready, boy," he says, ruffling the fur between the dog's ears.

Grabbing Titan's collar, Derek helps him to put his forepaws on the bed on either side of Stiles' ribs and grabs the base of his cock, just above the knot. Titan immediately attempts to fuck his fist, but Derek has a good enough grip that he doesn't find much success. He releases a low, rumbling growl, annoyed that his owner isn't allowing him to mate with his new bitch yet.

"I'll stop him from going too hard too soon, okay?" Derek tells Stiles, who has now released his legs and has his hands resting unsurely on Titan's shoulders.

The human nods. "Okay."

Derek disappears from sight, kneeling on the floor so he can peer between their bodies and guide the tapered tip of Titan's cock to Stiles' prepped hole. When Stiles first feels it he gasps and tightens up, temporarily undoing all of Derek's hard work, but after taking a few deep breaths he unclenches and feels the first couple of inches slip inside of his hole.

The dog jerks forward impatiently, wanting to be buried in him already, but Derek keeps his promise and maintains his grip on Titan's cock. Without Stiles even having to say anything, Derek knows when he is ready for more and feeds him a couple more inches. Maybe he is using his superior werewolf senses, or maybe he is using his own experience being fucked by Titan to make this easier on him. Whatever the reason, Stiles is glad because he doesn't think he would be able to form the words he'd need to check in with Derek if he tried.

He fists the fur on Titan's shoulders, careful not to hurt him, and stares up at his panting face, just living in the moment, revelling in his own debauchery. He has a dog inside of him. Even when he saw Derek getting fucked by Titan, even when he sucked Titan off, it hadn't quite felt real but like he was living some wonderfully dirty dream. Now, with Titan inching further and further inside of him, filling him up like Derek had mere minutes before, it feels real, especially when finally he feels the side of Derek's hand against his hole. Titan still moves his hips like he wants to fuck into him, but one stern word from his owner is enough to make him let up a little.

"Okay, just the knot's left," the alpha says.

Stiles exhales deeply.

"Think you can handle him yet?"

"Y-yeah, you can let go," Stiles assents, preparing himself.

Even with said preparation and with the multiple times he has seen what Titan can do with his cock, Stiles is still caught off-guard when Derek takes his hand away and the dog starts up a rapid pace. He clutches Titan tighter and cries out, wrapping his legs around Titan's hips and just holding on for the ride.

He has never been fucked this roughly before. Stiles doesn't know if he likes it or not at first, because he isn't really getting much pleasure. But then Titan adjusts himself, his forepaws just curling beneath Stiles' ribs, sharp claws leaving red scratches in their wake, and fireworks go off behind Stiles' eyelids. The pointed tip of Titan's cock batters his prostate, bringing out noises from him that he hadn't even known he could make, high-pitched whimpers and whines.

He didn't know his voice could go that high anymore, but you learn something new every day.

Stiles understands now why Derek had looked like he'd found heaven beneath Titan the first time he'd walked in on them.

Stiles certainly thinks _he_ has died and gone to heaven, and he never wants it to end.

There is almost too much stimulus, but he wouldn't change a thing about it. There's Titan's huge cock fucking in and out of him so fast that he doesn't even have time to miss it before it's back again, filling him to perfection. There's the feeling of the soft fur of Titan's belly rubbing against the insides of his thighs and his own hard cock, sending shivers down his spine.

Then there's Titan's hot breath blowing across his face, as the dog is so big that even while being mounted like this, their heads aren't far from each other. Stiles can smell a bit of dog food, but he has kissed Titan enough over the past few weeks that it doesn't gross him out anymore. It's an acquired smell, and he very much doubts that he could smell dog food now without getting hard.

When he opens his eyes, Stiles sees that Titan appears to be having the time of his life as well. The dog's long tongue hangs out of the side of his mouth and his eyes are bright and full of purpose. Stiles knows just what that purpose is—to knot him and impregnate him with his pups. Titan doesn't know any better. He doesn't know that Stiles doesn't have a womb and his seed will never catch, but he is sure that this won't stop Titan from gladly trying again and again, with both him and Derek.

"Oh God," Stiles whimpers, the image of his belly round and swollen with a litter of Titan's puppies entering his brain.

"Look at you two…even better than I imagined," Derek whispers from somewhere next to him.

Stiles turns his head to the side and locates the alpha standing next to the bed, his hand moving slowly across his cock. Stiles meets his eyes and licks his lips, a sign that Derek has no trouble reading.

The alpha gets on the bed and kneels next to Stiles' head, putting his cock in the perfect position for Stiles to suck. The human suckles on the head and slips his tongue beneath the foreskin, then he disentangles his left hand from Titan's fur and grabs one of the Derek's hairy ass cheeks to pull them closer, urging the alpha to go deeper.

Derek obliges, shuffling forward until most of his cock is in Stiles' mouth and then shallowly fucking it.

"Does he feel good?" Derek asks him. He can't really answer, but Derek doesn't expect him to, just keeps talking to him: "I bet it does. No, I _know_ it does. D'you see why I love getting reamed by him now, what I was talking about when I was prepping you earlier? He loves it, too. Look at him."

Derek waits for Stiles' bleary eyes to land on Titan's face to continue. "See how happy he looks? He's finally breeding his new bitch, finally claiming you as his. We belong together now, you, me and Titan. This is just the start, just you wait. Gonna be like this all the time, fuck each other all the time. Go on dates. I can't wait to take my two boys out and show you off. So good for me, taking Titan so well. Look so beautiful like this, baby…"

It's nonsensical, or at least Stiles can't make much sense of it. But it doesn't matter. He gets the gist, and that and being fucked at both ends is enough.

"You're close, aren't you?" Derek asks heatedly, reading him perfectly. "Gonna come on Titan's big doggy cock, aren't you?"

"Yes," Stiles says around Derek, but the word obviously comes out garbled and unintelligible.

He truly is. He can feel that familiar fire in his gut, burning brighter and brighter each time Titan thrusts into him, each time his prostate is nailed head-on and Titan's belly rubs against the glans of his cock, the tan fur matted with the pre-come he is generously weeping. Just before his orgasm hits, he stops sucking Derek off and instead smashes his lips against Titan's muzzle. The dog's thrusts falter momentarily in his surprise, but he is more than used to Derek making out with him while they have sex, so he swiftly gets with the programme and opens his maw.

It's with the taste of Titan's slobber on his tongue that Stiles comes. He scrunches his eyes shut and screams into Titan's mouth but makes no sound as he shoots between them, adding to the pre-come soaking the dog's belly fur. He clenches tight around Titan's cock, which spurs him on, making him fuck into his new human lover all the faster, jostling him about violently. Stiles is oblivious to all of this, his mind nothing but white noise.

Until he feels Titan's knot knocking against his rim, seeking entrance.

"D-Derek…he's gonna…" he chokes out.

"He's knotting you?"

"Yeah…"

"Just relax and take it, baby. It'll hurt at first, but you're gonna look so good hanging off it."

Stiles nods and picks his hands up from where he hadn't even realised they'd fallen to the bed. He threads the fingers of his right back through the fur on Titan's neck, but Derek takes his left in his larger one before he can do the same with it and squeezes reassuringly, giving him something else to ground himself with.

It's just in time, too. The very next second, Titan thrusts forward with enough force that Stiles' poor hole can't keep him out. In a flash of bright pain, Stiles is stretched wider than he has ever been stretched before and then the knot is in, his hole clenching reflexively around the very base of Titan's cock, locking them together. He can already feel the dog shooting deep inside of him, drenching his guts with watery doggy come, and when he focuses on this, he discovers that being knotted isn't altogether unpleasant. It still hurts, especially how the knot presses right up against his prostate in his overstimulated state, but as time passes and the pain lessens, he becomes certain that yes, he will definitely be letting Titan do this to him again.

Stiles isn't aware that he has tears in his eyes until Derek wipes them away with a soft cooing sound.

"You did so well, baby," the alpha murmurs, squeezing his hand again.

"Thanks…" Stiles, coming back to himself. He blinks the remaining moisture from his eyes and looks up at Derek, who is still hard. "Want me to take care of that?"

All at once the alpha's caring demeanour becomes mischievous. "Nah, I got it."

Stiles is nonplussed but says, "Okay," anyway.

For a while he lies there with Titan still on top of him. The dog doesn't get off of him at all, doesn't turn around so they are ass to ass like he probably would were he knotted with a proper bitch. Derek clearly has him trained to just hang out once he is tied, and Stiles can't find it in himself to complain. Honestly, the weight of the dog is comforting, as much as the feeling of his come sticking them together is a bit gross. Derek doesn't move either, just strokes a hand slowly up and down his cock, not to bring himself off but to keep himself hard.

"I thought you were gonna make yourself come," Stiles says tiredly, his confusion mounting further.

"Oh no. I never said that."

"Then what're you gonna do?"

Derek winks. "You'll see."

When the knot in Stiles' ass begins to shrink, Titan begins tugging on it lightly, testing to see whether he is able to pull it out yet. The movement stings but Stiles grits his teeth and bears it, and then with one hard yank from the dog, the knot and cock keeping him plugged up are gone and he feels dog come practically gushing out of his hole. He clenches his ass to keep as much of it inside as he can, not wanting to ruin Derek's mattress like he'd ruined his own.

"You can let it go if you want," the alpha says as he gets up from the bed, apparently able to read his mind.

"But…your bed."

"Look." Derek folds up the corner of the duvet and top sheet and tugs off the bottom sheet as well to reveal a thin plastic cover protecting the mattress. Despite how many times he has slept on top of it, Stiles had somehow never been aware of it before.

"Oh." Stiles clears his throat. "You're prepared for everything, aren't you?"

"Hey, you're not the only one who has accidentally ruined a bed by having too much fun on it."

"Still."

Derek appraises him before deciding something. "You wanna borrow a plug?"

"Uhh, yeah, sure," Stiles agrees.

The alpha goes over to his closet and crouches down to rummage through a trunk that is pushed into the back of it, hidden in the shadows so perfectly that Stiles hadn't even known it was there. He waits patiently, tilting his head to the side as he gets a look at Derek's asshole between his hairy cheeks, still stretched and sore-looking from when Titan had fucked it without prep. His cock twitches against his thigh but it's too soon for blood to actually fill it again, so Stiles ignores it and accepts the black butt plug that Derek soon brings him.

"Enjoy. That's my favourite one."

"It is?" Stiles asks, holding it up to inspect it. It's long and wide at the base. If he had to guess, Stiles would say it's just a tiny bit smaller than Titan's knot.

"Oh yeah. You should try wearing it sometime when you top. It's awesome."

"You've worn this?"

"Many times."

That's all the answer Stiles requires. He wipes his fingers between his cheeks and uses the dog come he gathers to slick up the plug before gently sliding it inside of himself. He winces at the widest part, but then it goes in smoothly and keeps him nice and filled, like Derek said it would. Plus, having a sex toy inside of him that has also been inside of Derek does things to him.

After putting things back in place, Derek grabs the lube and walks over to where Titan now lies on his dog bed, cleaning off his cock.

"Titan," Derek barks, flashing his eyes. "Present."

Of all the sick things that Stiles has witnessed and done over the past few months, there is apparently still further into Hell to fall.

Under the watchful gaze of both Stiles and Derek, Titan gets up from his bed, turns his behind to the alpha, stretches out his forelegs so that his lower half is raised higher than his upper half and then lifts his tail in the air. From his position on the bed, Stiles has a great view of Titan's little doggy asshole, the light-pink skin surrounded by tan fur. He never thought he would see it in this sexual context. He thought that Titan just topped Derek and would keep exclusively topping both of them, while he and Derek would top each other. But apparently not.

"You're not really doing what I think you're gonna do, are you?" Stiles asks Derek.

Derek gets down on his knees and meets the human's eyes, dropping the lube next to him on the floor. "What do you think I'm going to do?"

"You're gonna…fuck him, too?"

"Oh yeah. I really am. Enjoy the show, baby."

Stiles flicks his eyes back and forth between Titan's small asshole and Derek's big cock and feels worried. "But can he take you?"

"Of course he can. He's taken me many times before and loved it."

"R-really?"

"Just watch. You'll see."

Enraptured, Stiles gapes as Derek lowers himself to his hands and brings his face close to Titan's asshole. He just hovers there, eyes closed, inhaling audibly and moaning like the animal musk he must be smelling is amazing.

"That's kinda gross, dude," Stiles says with a frown.

"It's fine," Derek mumbles. "He's already been out to do his business and I cleaned him after."

Still frowning, Stiles nevertheless shuts up and lets Derek do what he wants. Who is he to try to stop him?

"You'll have to do this sometime," Derek says next, in between inhales. "See what the fuss is about."

Stiles isn't sure, but he wasn't sure about letting Titan fuck him either and Derek was right about how fantastic that felt. The alpha hasn't lead him wrong yet, so he nods. Then he realises that Derek can't see him and says a quiet, "Maybe."

Finally, once he has smelled his fill, the werewolf closes the small gap between himself and Titan's asshole. He rubs his nose around the puckered skin and moans again when Titan pushes back against his face, either because he enjoys the stimulation or because he has learned from previous times Derek has done this that it's what his owner wants him to do. Derek rubs his nose one last time over Titan's asshole and then presses his lips to it in an almost tender kiss—the same way he has kissed Stiles in the past.

Stiles, even though he still harbours some disgust, is turned on all over again.

After a few seconds of this, Derek starts to move his lips and basically makes out with Titan's asshole. Titan apparently approves of this, because he stretches his forelegs out even more to better present himself and his tail wags in the air above Derek's head, the breeze it creates blowing through the alpha's dark hair.

"We're both totally going to Hell," Stiles says, standing up to get a closer look.

Derek takes his mouth away from Titan just long enough to say, "Gladly," before he is right back at it. He swirls his tongue around the dog's asshole and prods at it with the tip, coaxing it to open up and let him inside. It doesn't happen right away, but Derek is nothing if not persistent and Stiles gasps when he sees Derek's tongue finally partially disappear into Titan's body. His legs are shaky from his earlier fucking, so he sinks ungracefully to his knees and then sits down heavily, grunting when the harsh movement causes the plug to shift inside him.

Blindly, Derek fumbles for the lube, pops the cap and slicks up his fingers. "Gonna make quick work of this 'cause I need to get inside him ASAP."

One by one, Derek wedges four fingers inside Titan's asshole. The dog doesn't so much as whine, just keeps his tail wagging in the air and pants happily. Once he deems Titan ready, Derek extracts his fingers, runs them over his cock to slick himself up and then aims the tip at the dog's shiny asshole.

"Ready for a show?" Derek asks Stiles, hazel eyes gleaming.

God help him, Stiles is. "Fuck yeah."

Derek enters Titan much faster than he'd entered Stiles, his hands gripping Titan's haunches to hold him in place. Stiles almost feels bad on Titan's behalf because that has to hurt, but again the dog doesn't seem to care. Derek starts thrusting immediately, his heavy balls softly hitting Titan's furry ones as Titan's tail brushes back and forth across his abs. Settled into a slow rhythm now, Derek removes his hands from his dog's haunches and plays with his own nipples, tipping his head back as he twists and pinches them between his index fingers and thumbs so hard it must be painful.

"So tight," he moans, his eyelids fluttering.

Stiles, unable to resist the vision that is the muscles of Derek's body flexing with each thrust, moves closer and fists the hair on the back of his head. He turns Derek's face toward him and captures his mouth in a kiss, not giving a damn when he realises he can taste Titan's ass on the alpha's tongue. He bats Derek's hands away from his chest and runs his fingers through Derek's chest hair, delighting in the feel of it before he takes over for the deputy and flicks and tweaks his nipples, wanting— _needing_ —to help him come inside Titan's doggy ass.

His words from a few minutes ago ring true, as he is definitely condemning himself to Hell by enjoying this so much, by his disgust vanishing and being replaced by pure enjoyment and a surge of arousal big enough to have his cock hardening again.

"Stiles…" Derek groans against his lips. "Fuck me."

Drawing back, Stiles has to make sure he heard the werewolf correctly. "What?"

Derek stops thrusting, staying buried to the hilt inside of Titan. "I want you to fuck me. You can see what I meant about the plug."

There is no way Stiles is turning down an offer so good.

Picking up the lube from where Derek dropped it, Stiles makes his way behind the alpha and pushes at his shoulder blades, right over his triskelion tattoo, to get him to lean forward and present his ass to him like he'd ordered Titan to do earlier.

It's a thing of unparalleled beauty, just like everything else about Derek. His ass is firm, muscular and hairy, with a delicious curve to his cheeks that Stiles is sure makes everybody he meets want to reach out and squeeze them. That's exactly what Stiles does now, fitting each hand around one hairy cheek and testing their musculature. He has seen Derek working out before, so he is aware that the alpha doesn't slack when it comes to doing squats. The results are nothing short of delicious.

"Gorgeous," he compliments, dribbling some lube down the hairy crack.

"Get on with it already," Derek says impatiently, looking back over his shoulder.

Stiles narrows his eyes, but then it becomes clear that Derek isn't the only one who wants him to get on with things. Titan wiggles about, trying to get his owner to resume fucking him, and Stiles doesn't have the heart to deny him such a thing for any longer than he has to. He makes quick work of prepping Derek. He doesn't even have to do that much because the results of Titan mounting him earlier are still mostly present, Derek's superior healing ability apparently not working on his stretched asshole. Or maybe Derek purposefully stopped it from working this time. Stiles is glad because, if he is honest with himself, he wants to get inside Derek's hairy little asshole like, yesterday.

With glee, Stiles presses the head of his re-hardened cock against Derek's hole and pushes inside. He knows the alpha can take it, so he isn't particularly gentle. He gives a couple of thrusts, familiarising himself with the warmth of the alpha's silky walls, and then Derek straightens his back and takes over, fucking himself back on Stiles' cock and then his own cock forward into Titan's ass.

As with everything, Derek moves a grace and a fluidity that Stiles could never hope to match. He wraps his arms around the deputy's body and locates a nipple with his right hand. He twists it again, making sure the soreness doesn't have time to heal, and with his left hand he slides it down Derek's abs until he reaches his untamed pubes. He divides his fingers so that two of them end up on either side of Derek's cock, feeling how Titan's asshole grips it every time he sinks home.

Derek wasn't kidding when he said it was tight.

He rests his forehead against the back of the alpha's neck and just breathes, just _feels_. The hole around him is so warm and welcoming and the burning heat of Derek's body as he moves is more than enough to have him sweating even though he isn't really doing much himself. He keeps kneeling there and looks down the length of Derek's broad back, watching as Derek fucks himself on his cock.

It's an entrancing sight, and Stiles never wants it to end. Of course, it's when he thinks this that it does.

"I'm close," Derek warns him.

"Me, too." Stiles removes his left hand from Derek's pubes, runs it back up his torso and plays with his other nipple again.

It works. Derek thrusts back and forth between them a few more times and then sinks all the way inside Titan's hole as he comes, his own hole clamping tight around Stiles' cock. Stiles takes over thrusting now, both to prolong Derek's orgasm and make it more intense and to reach his own for the second time as well. The thought of the alpha filling Titan's doggy hole with his thick come is all it takes for Stiles to fill Derek up, too, all but collapsing against Derek's back. He drops his hands from the deputy's nipples and wraps them around his middle, holding on.

For just over a minute, all three of them stay exactly as they are. Then, when Stiles is able to move again, he pulls out of Derek, come dripping in his wake. This allows Derek to do the same with Titan, but he only moves away far enough for him to get down on his hands and stick his gorgeous hairy ass out, a quick glance over his shoulder making it clear to Stiles that he wants to be eaten out. How could Stiles possibly say no to that?

It's ridiculously hot, eating his own come out of Derek's used hole. He seals his lips around the rim and sucks as much as he can from the alpha's body, also using the tip of his tongue to basically scoop it out. When he thinks he has got as much of it as he can, Stiles reluctantly moves his face away from Derek's ass and goes to the side so that he can watch Derek finish up with Titan.

Derek looks just as into rimming his dog as he was before, luxuriating in it, making it last. His face is a mess of his own come, his dark beard slathered.

"You're ridiculously disgusting," Stiles comments.

Derek opens one eye to peer up at him. "And?"

Stiles grins. "And I wouldn't change a thing about it."

When Derek finishes eating Titan out as well, he wraps his hand around the back of Stiles' neck and looks questioningly at him.

"What?" Stiles asks.

Derek explains by opening his mouth and letting him see the come he has on his tongue.

Stiles inhales sharply through his nose. "Fuck yes."

The kiss is probably the messiest he has ever had. Not even his first proper make-out session was like this, when both him and the girl he was seeing at the time were still learning how and were failing spectacularly. Derek pushes his come into Stiles' mouth with his tongue and then they swap it back and forth. While he was never one to swallow before he met Derek and Titan, there is no doubt in Stiles' mind that he loves the taste of it now, probably purely because it's Derek's come he is tasting.

When the kiss ends, Derek and Stiles both just kneel there smiling at each other like fools.

"So…what did you think?" the alpha asks, though he looks like he already knows the answer.

Stiles replies anyway. "That. Was. _Awesome_ ," he says.

"So you definitely want to be in this relationship?"

"I really do."

Derek's smile softens. "I'm glad."

Stiles kisses him chastely again and whispers, "I love you," against his lips. He doesn't expect Derek to actually say it back, but he does.

* * *

The very next week, Stiles packs up all of his things and moves out of his apartment and right into Derek's house. Derek helps, using his superior werewolf strength to lift the boxes that Stiles wouldn't have a hope in Hell of shifting on his own, and they manage to get it done in several trips over the course of a single day.

By that evening, Titan is curled up in a huge heap in the space between the living room sofa and the coffee table, likely wanting to be close to both of his lovers. Derek tells Stiles that Titan is the sentimental sort from where he sits in his usual place on the living room sofa, while Stiles is stretched out across it, his head in the alpha's lap. Both of them are still sweaty from the effort it took to relocate all of Stiles' possessions, but neither of them can be bothered to move.

"I can't believe this is my life," Stiles murmurs, disturbing the quiet.

Derek hums, wordlessly asking him to go on.

"I just mean I never thought I'd be here a year ago, in love and living with an amazing man and his dog."

"Kind of a head trip, huh?" Derek guesses.

"Yeah. I'm not complaining, though."

"You better not be," Derek says teasingly.

"Oh shut up."

Neither speaks again for a few minutes, just the sounds their breathing and Titan's soft snores filling the silence. Then Derek cups the side of Stiles' face, strokes his thumb gently across his cheekbone and says the best two words Stiles has ever heard:

"Welcome home."

**Author's Note:**

> So, I'd already done pseudo-bestiality a couple of times in previous instalments of this series, where Derek fully shifts into a wolf or shifts into an alpha form and fucks Stiles with his big lupine cock, but I hadn't done true bestiality yet and wanted to. So this happened. It ended up being much longer than I anticipated, but that's just the way this series goes for me sometimes—especially when I'm writing something that gets my motor running as much as this did. I regret nothing! :D
> 
> Up next, I'll be filling a prompt in which Derek, a teacher and dom, gives detention to his bratty student, Stiles.
> 
> **P.S. Don't forget to subscribe to me to be notified when my future fics go live, which will all be Sterek. And please check out my past fics if you haven't already and are interested.**


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